Power management in mobile embedded systems, such as cell phones, PDAs, and other wireless/portable systems, is considered to be one of the 5 major design challenges by the semiconductor industry forum. Over the next 12 years, the active element (transistor or gate) will get 4 times smaller in length, with the gate count increasing 16 fold, and even with the best power management features, both in software and hardware, a battery budget deficit of 25 fold will ensue. To put things in perspective, to run all the applications (internet, videoconferencing, multimedia, games, etc.,), the system will need to supply power of 2.5 W, while for reasonable battery life of a few days of operation one could not exceed 0.1 W. This is an enormous challenge. The semiconductor industry has always exceeded the goals it set for itself in the past, and we expect the same thing will happen again. A comment is in order here: One needs to distinguish power aware and low power systems. A power-aware system may tradeoff speed against power dissipation as needed at the moment, while maintaining long-term low power strategy. For example, a human may sprint from a source of violence, thus expending energy, while maintaining a low average metabolism during other periods. The key is that the human had the ability to sprint fast when it was warranted. A low power system may be compared to a human who is too energy restricted to rise to the challenge of an imminent attack.
There are examples of the need for improved power systems. Microsoft has released WinCE.net, which is rapidly becoming the de facto standard operating system of mobile systems. WinCE, the earlier version, monitored power dissipation of the entire system and selectively allowed some subsystems to go into sleep or low power modes. However, with the advent of WinCE.net, the concept of scalability has been introduced, allowing the designer to choose the level of power management they wish to use. In addition, scalability has come to peripherals as well. As such, in place of a few discrete states of power dissipation, a device could now potentially have many intermediate levels of power dissipation, used judiciously with a long-term perspective of maintaining battery power for long life. Thus, it is no longer the issue of coarse-grain control of the subsystems, but fine-grain control by the OS (WinCE.net) and self -adaptation by the devices.
This need opens up significant opportunities for dynamically reconfigurable hardware with the intent to adjust, in real-time, the QOS (quality of service) metrics to get the most reasonable result to the end user. Though coordination between software and hardware engineers has always been a challenge, we expect that the Microsoft model of full support for developers will overcome this challenge. It is noted, however, that no chip designers have yet embraced the concept of dynamic reconfiguration to save power or tradeoff power against speed. This will change as more pressure is brought from both the consumer and developers, such as Microsoft.